The present disclosure relates to prostheses for the lower limb of a person and particularly to an improvement for the engagement of a prosthetic foot to a lower limb prosthesis.
One form of lower limb prosthesis 10 is shown in FIG. 1 which includes a lower leg or transfemoral pylon 12, connected at its upper end to a prosthetic knee joint 14 and at its lower end to a prosthetic foot 18. The knee joint is connected to a socket 16 adapted for a secure fit to the intact proximal limb. It is understood that the pylon 12 may be part of a total limb prosthesis system. The lower leg pylon 12 is connected to the prosthetic foot 18 by a prosthetic ankle joint 20 as is known in the art.
The foot prosthesis 18 shown in FIG. 1 represents a “low energy” prosthesis in the sense that the foot prosthesis is generally rigid. The prosthesis 18 does not have the ability to flex or the ability to absorb and return energy in flexion in the manner of a physiologically normal foot. Consequently, more active lower leg amputees may desire a “high energy” foot prosthesis, such as the prosthesis 30 shown in FIG. 2. The prosthesis 30 includes a foot plate 32 that is curved upward to an ankle plate 34. The ankle plate 34 includes mounting elements 36 for attaching the foot prosthesis 30 to an ankle joint or a lower leg pylon in a known manner. The foot prosthesis 30 further includes a heel plate 38 fastened to the foot plate 32 in a known manner. The foot plate and the heel plate are curved and configured to flex in the manner of a leaf spring. The foot plate 32 and heel plate 38 thus absorb energy as the person applies his/her weight to the foot prosthesis, thereby flexing or bending the plates. This energy is returned as the plates act as a leaf spring to return to their original unflexed state.
Such “high energy” foot prostheses are desirable for active persons, such as athletes and children. Foot prostheses of the type shown in FIG. 2 are readily adapted for amputees of normal or taller stature due to the overall dimensions of the prosthetic foot necessary to provide sufficient functionality. However, these necessary dimensions of the prosthetic foot make “high energy” prostheses problematic for persons of smaller stature or amputees with longer residual limbs such as long transfemoral amputees, long transtibial amputees, and Symes amputees, that are limited to a low “build height” for the lower limb prostheses. These amputees are often limited to choosing a prosthetic knee capable of high activity levels or a prosthetic foot capable of high activity levels, but not both.
There is a need for a lower limb prosthesis system that allows the smaller stature amputee and the longer residual limb amputee to enjoy the benefits of high energy, high activity prostheses. There is also a need for a prosthesis system that allows the person to readily swap foot prostheses between “low energy” and “high energy” prosthesis as the occasion dictates.